Anyone know the origin of ‘dibs’… as in “I’ve got dibs on that”, meaning that the
speaker can somehow claim it as his/her own

Take a look at Michael Quinion’s site:

http://www.worldwidewords.org/qa/qa-dib1.htm

We also covered it on the old board but as Yuku search for the old forum is still as dead as a dodo and they haven’t even acknowledged yet the two reports I’ve submitted then the rest is silence, at least for now.